Getter supply



Get. 13, 1964 1-. A. CQNN R 3,152,689

4 GETTER SUPPLY Filed Sept. 19, 1962 INVENTOR 72/04/454 60mm? Arm/w; s

United States Patent 3,152,689 GETTER SUPPLY Thomas A. Connor, Hilton, N.Y., assignor to Consolidated Vacuum Corporation, Rochester, N.Y., a corporation of New York Filed Sept. 19, 1962, Ser. No. 224,785 5 Claims. (Cl. 206-.4)

The present invention relates to getter supplies and, more particularly, to a getter supply for ion-getter pumps.

Ion-getter vacuum pumps are well known in the art. Pumps of this type usually comprise means for ionizing residual gas molecules in a pre-evacuated space, and means for supplying into such space a material capable of gettering the ionized gas molecules. In a frequently employed pump of this type, the ionizing and the getter supply means are housed in an envelope adapted to be connected to a vacuum vessel, and the getter supply means are permitted to form a molecule-entrapping layer of getter material on an inner surface of such envelope. For pumps of smaller to average capacity, the getter supply most widely employed is a getter supply of the resistance-heated type, i.e. a getter supply comprising an electrically energized element having the getter material disposed thereon or located in close proximity thereto.

So far, these getter supplies have constituted one of the most vulnerable par-ts of the present pumps. Thus, the aforesaid heater elements usually had an average lifetime smaller than the other elements of the pump. Consequently, these pumps frequently had to be disassembled or discarded before their getter supply was actually exhausted. In addition, single erroneous operation by an inexperienced operator could render an entire pump useless. In either case, expensive getter material and valuable time and labor was lost and the evacuation process had to be interrupted, which frequently resulted in further waste.

The present invention overcomes these disadvantages by providing a getter supply comprising at least five spaced terminal means distributed substantially along the periphery of a circle and at least one wire comprising a getter material. According to the invention, this wire is suspended by and extends between the aforesaid terminal means to define a plurality of mutually spaced wire sections arranged in a star-like pattern.

' The term star-like pattern used herein is meant to refer to a pattern which is composed of a plurality of lines which extend substantially diagrammatically across a polygon from the corners thereof.

Thus, if the number of the above-mentioned terminals is five, the star-like pattern referred to has the form of a five-pointed star of the type known as pentacle or pentagram. In this case, the above-mentioned terminals are located in the points of such pentacle and the aforesaid wire sections define the pentacle. Insulation between these wire sections may be achieved by spacing such sections in a direction substantially perpendicular to the plane of the pentacle.

Star-like patterns with more than five points can be formed by employing six, seven or more spaced terminal means distributed substantially along the periphery of a circle.

If an even number of terminal means is used, the starlike pattern defined by the aforesaid wire sections will have an open side, while a complete star-like pattern will result if an odd number of terminal means is used. The expression star-like pattern is also intended to cover these star configurations with an open side, as well as the latter complete star-like patterns.

One advantage of the getter supply of the invention resides in the fact that a plurality of independently energizable getter sources in the form of the aforesaid wire heater wire.

3,152,689 Patented Oct. 13, 1964 ice sections is available for the distribution of getter material to the pump elements. Thus, the above-mentioned wire sections can be energized singly or in a plurality of predetermined combinations. For instance, the getter supply and adjacent parts of the pump can be pre-heated by connecting the wire sections in the form of one or more series branches to a power source. Subsequently, any one of the wire sections can be energized to release getter material by direct connection thereof to such power source. Should one or more wire sections fail, the electrical connections to the terminal means could be altered to energize one or more of the remaining wire sections.

In addition, due to the arrangement of the aforesaid Wire sections in a star-like pattern, each wire section extends substantially diametrically across the circle on which the terminal means are arranged. In this fashion, each wire section covers an optimum area for the dis tribution of getter material, especially when the pump envelope is cylindrical and the terminal means are arranged along the inner cylindrical surface of such pump envelope.

It will be appreciated that the wire sections extend closer and closer to diameters of the aforesaid circle as the number of terminal means located in the points of the resulting star-like pattern is increased. In addition, while one wire, extending from terminal means to terminal means, may be used for forming the star-like pattern, a number of separate wires could also be employed to define such star configuration. Thus, in a preferred embodiment of the invention I employ seven terminal means distributed substantially along the periphery of a circle, and seven mutually spaced Wires comprising a getter material and being suspended by and extending between the terminal means in a star-like pattern. The wire or wires used in the getter supply of the invention may comprise an electric resistance heater wire having applied thereto a getter material. This heater wire should be of a material having a melting point higher than the evaporation temperature of the getter material.

Thus, in a preferred embodiment of the invention, I employ a heater wire or heater wires of tungsten.

The type of getter material used will depend on the nature of the pump and the gas to be pumped. Thus, any suitable material currently employed for gettering purposes such as titanium, zirconium, tantalum, barium, cerium and cerium alloys, for instance, could be used. The getter material which has proved most widely applicable so far is titanium.

Thus, in a preferred embodiment of the invention I use a wire or wires of titanium disposed in contact with the Preferably these titanium wires are entwined with the aforesaid tungsten wires to form a cable of titanium and tungsten wires.

After testing many configurations, I have obtained most favorable results with a cable composed of three strands of tungsten and four strands of titanium. In such cable, one of the strands of tungsten forms the central cable strand or core of the cable and the other tungsten strands are located adjacent such central strand or core. The titanium strands are arranged in the form of two pairs of strands having said tungsten strands located or interposed therebetween. Preferably, the aforesaid strands of tungsten and strands of titanium are of equal diameter. In this manner, a getter supply cable is obtained which has a very even and stable form and which displays little tendency to cause formation of undesirable balls or nodules of titanium.

It should be' understood that getter materials other than titanium and refractory or heat-resistant metals other than tungsten may be used for forming the aforesaid cable.

The invention will become more readily apparent from the following detailed description of a preferred embodiawaaea ment thereof, illustrated by way of example in the accompanying drawings, in which:

FIG. 1 is a side view, in section, of an ion-getter vacuum pump embodying the invention;

FIG. 2 is a view along lines 11-11 in FIG. 1; and

FIG. 3 is a cross section through one of the wires shown in FIGS. 1 and 2.

The ion-getter vacuum pump 11) illustrated in FIGS. 1 and 2 has an enclosure 11 of a suitable material, such as glass. Enclosure 11 is provided with a pipe or nipple member 12 for connection of the space within enclosure 11 to a vacuum space, such as the space within a preevacuated vessel (not shown) containing residual gas molecules.

Arranged within housing are a cathode or filament electrode 14 and an anode or grid structure 15. In the embodiment shown, the anode structure is formed of a piece of wire mesh material which is bent to have a hollow-cylindrical configuration. Anode structures of this type are well known.

While only one filament 14 has been shown, a plurality of independently energizable filaments could be used so that the evacuation process need not be interrupted if one filament should fail.

Filament 14 is mounted on a pair of mounting and terminal means 16 and 17 extending through enlosure 11, and anode structure is mounted on a mounting and terminal means 18 sealably extending through a lateral protrusion 19 of enclosure 11.

A getter supply 30 embodying the invention is also disposed in enclosure 11.

. This getter supply 30 comprises seven terminals 1, 2, 3, 4, 5, 6, and 7 (see FIG. 2). It will be noted that the section through the pump in FIG. 1 has been carried out so that some of these terminals, namely terminals 4, 5, 6, and 7, are fully visible in FIG. 1. Terminals 1 and 2 are partially visible in FIG. 1.

The aforesaid terminals 1 to '7 extend through enclosure 11 and have attached thereto a plurality of wires or cables 20, 21, 22, 23, 24, 25, and 27, in a manner such that wire 20 extends between terminals 1 and 4, wire 21 between terminals 4 and 7, wire 22 between terminals 7 and 3, wire 23 between terminals 3 and 6, wire 24 between terminals 6 and 2, wire 25 between terminals 2 and 5, and wire 26 between terminals 5 and 1 (see FIG. 2).

As is apparent from FIG. 2, these wires 20 to 26 define a seven-pointed star-like pattern 32. As shown in FIG. 1, the wires 20 to 26 are mutually spaced in a direction substantially perpendicular to star pattern 32.

It will be appreciated that the wires 20 to 26 could be sections of one and the same wire which extends from terminal 1 to terminal 4, and from terminal 4 to terminal 7, etc., in the manner shown for wires 20 to 26.

It will also be appreciated that the wires 20 to 26 or the sections of the aforesaid one wire need not necessarily extend exactly perpendicularly to terminals 1 to 7, as long as the wires or wire sections are prevented from normally contacting one another in the center region of star pattern 32.

The wires or cables 20 to 26 comprise an electric resistance-heater wire having a getter material disposed thereon. FIG. 3 shows a preferred form of these wires or cables 20 to 26 by means of a cross section through wire or cable 20.

As is apparent from FIG. 3, wire 20, as well as the other wires 21 to 26, is in the form of a cable which is composed of seven strands 36, 3'7, 38, 39, 40, 41, and 42. The center strand or core 37 of cable 35 is made of tungsten (W), and two outer strands 36 and 38 of cable 35 are also made of tungsten (W). The remaining strands 35, 39, 40, and 42 of cable 35 are made of titanium (Ti). All strands 36 to 42 are of substantially equal diameter.

Considering FIG. 3, it will be appreciated that tungsten strands 36 to 38 present a large heat-transfer area to titanium strands 39, 40, 41, and 42, and present also a large surface area on which molten titanium can flow and distribute itself. In addition, tungsten strands 36 and 37 and 37 and 38 define narrow grooves therebetween into which molten titanium is drawn by surface tension so that the formation of titanium balls or nodules on cable 35 is avoided.

Prior to the regular operation of the pump shown in FIGS. 1 and 2, the wires or cables 20 to 26 can first be energized so that undesirable gas residues are driven therefrom and from adjacent areas. After such degassing operation, at least one of the wires 20 to 26 can be energized to release into the space within enclosure 11 a supply of getter material, i.e. titanium, which will form on inner surface portions of enclosure 11 an ion-entrapping layer schematically indicated at 45.

To this end, the electric circuit 50 shown in FIG. 2 may be employed. This electric ciruit 50 comprises a source of electric power 51 which has been illustrated as a battery but could also be another type of direct-current source or also an alternating-current source. Electric circuit 51) also includes a first conductor 53 extending from one terminal of source 51 to terminal 1 of getter supply 30. A main switch 52 is interposed in conductor 53 so that the energization of getter supply 30 may be completely interrupted whenever necessary or desired. Another wire 54 extends from the other terminal of source 51 to the input of a double-throw switch 60 having two outputs connected respectively, by conductors 61 and 62 to terminals 3 and 4 of getter supply 30.

If the switch 60 is in the position indicated in FIG.

2 by a solid line, a first series circuit comprising wires 23, 24, 25, and 26, is connected in parallel to a second series circuit comprising wires 20, 21, and 22 across source 51. In this manner, wires 20 to 26 are heated to a temperature insufficient to cause getter evaporation, but sufficient to carry out the aforesaid degassing operation.

. After completion of the degassing operation, switch 60 is moved to its position indicated in FIG. 2 in dotted lines. This causes energization of wire or cable 20 alone. In this manner, wire or cable 20 will be sufficiently energized to release titanium getter material into the space within enclosure 11, and a layer of ion-entrapping getter material schematically indicated at 45 will be formed. During or after energization of wire or cable 20, operation of pump 10 is initiated by connecting a source of heating current 70 to filament terminals 16 and 17 and a suitable source of plate potential 71 between one of the filament terminals 16 and 17, such as terminal 17, and anode terminal 18. This aspect of the operation of pump 10 is well known. Thus, an electric discharge will be established in enclosure 11 in which residual gas molecules present therein will be ionized and ultimately driven onto layer 45 and securely entrapped therein.

Depending on the capacity of power source 51 and of the getter material requirements of pump 10, more than one of the wires or cables 20 to 26 could, of course, be energized at a time to release getter material.

Should one or more of the wires 20 to 26 fail, the power connections to the terminals of supply 3%} are suitably altered so that the remaining ones of wires 26 to 26 may be rendered operative, as desired.

If desired, the ion-entrapping properties of layer 45 can be improved by negatively biasing layer 45 with respect to filament 14, such as by means of a battery 8%) connected between filament terminal17 and a terminal means '81 which is in contact with layer 45.

The getter supply 30 could serve as a getter primer which is only actuated prior to or at the start of the pumping operation, or could also serve as a getter supply effective during the pumping operation.

Other applications of the getter supply of the invention and various modifications thereof within thescope of the invention will suggest themselves to those skilled in the art.

I claim:

1. A getter supply for an ion-getter vacuum pump, comprising at least five spaced terminal means distributed substantially along the periphery of a circle, and at least one wire comprising a getter material, said wire being suspended by and extending between said terminal means to define a plurality of mutually spaced wire sections arranged in a star-like pattern.

2. A getter supply for an ion-getter vacuum pump, comprising seven spaced terminal means distributed substantially along the periphery of a circle, and seven mutually spaced wires comprising a getter material, said wires being suspended by and extending between said terminal means in a star-like pattern.

3. A getter supply for an ion-getter vacuum pump, comprising at least five spaced terminal means distributed substantially along the periphery of a circle, and at least one cable comprising strands of a getter material and strands of a metal having a melting point higher than the evaporation temperature of said getter material, said cable being suspended by and extending between said terminal means to define a plurality of mutually spaced cable sections arranged in a star-like pattern.

4. A getter supply for an ion-getter vacuum pump, comprising seven spaced terminal means distributed substantially along the periphery of a circle, and seven mutually spaced cables comprising strands of a getter material and strands of a metal having a melting point higher than the evaporation temperature of said getter material, said cables being suspended by and extending between said terminal means in a star-like pattern.

5. A getter supply for an ion-getter vacuum pump, comprising at least five spaced terminal means distributed substantially along the periphery of a circle, and at least one cable composed of three strands of tungsten and four strands of titanium, said cable being suspended by and extending between said terminal means to define a plurality of mutually spaced cable sections arranged in a star-like pattern.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A GETTER SUPPLY FOR AN ION-GETTER VACUUM PUMP, COMPRISING AT LEAST FIVE SPACED TERMINAL MEANS DISTRIBUTED SUBSTANTIALLY ALONG THE PERIPHERY OF A CIRCLE, AND AT LEAST ONE WIRE COMPRISING A GETTER MATERIAL, SAID WIRE BEING SUSPENDED BY AND EXTENDING BETWEEN SAID TERMINAL MEANS TO DEFINE A PLURALITY OF MUTUALLY SPACED WIRE SECTIONS ARRANGED IN A STAR-LIKE PATTERN. 